Pogo pins are widely used in inspection devices or sockets for semiconductor wafers, LCD modules, and semiconductor packages, and battery connectors for cell phones.
FIG. 1 illustrates a conventional pogo pin 6.
Referring to FIG. 1, the pogo pin 6 includes a cylindrical pin body 11, a coil spring 14 inserted in the pin body 11, and upper and lower probes 12 and 13 disposed at both ends of the coil spring 14.
FIG. 2 is a cross-sectional view of a conventional socket used in inspecting a semiconductor package. In FIG. 2, the pogo pin is used to establish a connection between an external terminal of the semiconductor package and a metallic wire on a printed circuit board.
Referring to FIG. 2, the socket 20 includes pogo pins 6 and a main body 1. The pogo pin 6 is used to establish an electrical connection between an external terminal 3a of a semiconductor package 3 and a contact pad 5a of a test board 5. The main body 1 is used to support the pogo pins 6 so that the pogo pins 6 may be arranged at regular intervals and be protected from deformation or damage.
The pogo pin 6 includes a pipe-shaped pin body 11, a metallic upper probe 12, a metallic lower probe 13, and a coil spring 14. The upper probe 12 is coupled to a top side of the pin body 11 to come into contact with the external terminal 3a of the semiconductor package 3. The lower probe 13 is coupled to a bottom side of the pin body 11 to come into contact with the contact pad 5a of the test board 5. The coil spring 14 is disposed in the pin body 11 and comes into contact with the upper and lower probes 12 and 13 to allow the upper and lower probes 12 and 13 to elastically come into contact with the external terminal 3a of the package 3 and the contact pad 5a of the test board 5, respectively, when inspection is conducted.
The pogo pin 6 is preferably small in size so as to be suited to increasingly miniaturized and integrated semiconductor packages. A reduced distance between the external terminals 3a inherently leads to a decrease in the outer diameter of the pogo pin 6. Further, the pogo pin 6 needs to be minimized in length to reduce electrical resistance between the semiconductor is package 3 and the test board 5.
For instance, in order to reduce the distance between the semiconductor package 3 and the test board 5 to 0.95 mm or shorter, the pogo pin 6 needs to have a length of 0.95 mm or shorter accordingly.
On the other hand, in order to securely establish electrical contact between the external terminal 3a of the semiconductor package 3 and the upper probe 12 and between the contact pad 5a and the lower probe 13, the range of motion of the upper probe 12 and the range of motion of the lower probe 13 are preferably as large as possible. However, in the case of a conventional pogo pin with a size as small as 0.95 mm or shorter, providing a sufficient range of motion is not possible.
For example, in the case of a pogo pin with a length of 0.95 mm, the coil spring 14 can have a range of motion of no more than about 0.6 mm, except for a space for the upper and lower probes. In this case, a coil spring of ten turns each having a diameter of 0.06 mm takes up at least 0.6 mm. On the other hand, a reduced diameter of a coil spring may result in a decreased spring force or electrical signal loss. Besides, a decreased number of turns of a coil spring may not provide a sufficient range of motion within a limited range of elasticity of the coil spring.